This invention relates to an apparatus and method to extract material from a running length of fiber. Particularly, this invention can be used to extract a pre-spinning polymer solvent from a solution spun fiber by solvent to solvent extraction in a conduit by moving a continuous running length of the fiber through the conduit and flowing the extraction solvent through the conduit to remove the pre-spinning polymer solvent from the fiber.
A prior method to extract mineral oil from polyethylene solution spun fiber and a method to manufacture such fiber is disclosed in U.S. Pat. No. 4 413 110 hereby incorporated by reference. A prior art method for treatment of filamentary materials in a tube is found in U.S. Pat. No. 2 509 279.